I've always had the same thing, and im sure everyone else has. I'm sure its completely normal and pretty sure that environment plays a role in it. For example if you're cold and you grab your bicep, you will see the imprint more clearly than at a room temperature environment. The only thing I really know about the whole blood flow thing is that when you squeeze one of your fingers and the pink doesnt come back within a few seconds. Its a good hint that you're dehydrated.